No module named ‘openpyxl’ – Python 3.4 – Ubuntu

@zetysz and @Manish already fixed the problem. I am just putting this in an answer for future reference:

• pip refers to Python 2 as a default in Ubuntu, this means that pip install x will install the module for Python 2 and not for 3
• pip3 refers to Python 3, it will install the module for Python 3